An inode stores basic information about a regular file, directory, or other file system object. It contains a list of direct, indirect, and doubly and triply indirect pointers. On some FileSystems, very small files can be stored directly in the Inode itself.

Sophisticated FileSystems create Inodes on demand, but with most, the number of Inodes on a Partition has to be decided on during FileSystem creation. It is rare to run out of Inodes unless you have an unusual usage profile such as storing a news spool or Squid cache. Exhaustion of the inodes will prohibit the creation of additional files even if sufficient HDD space exists.

How many Inodes do I have free?

• df - i

What information does an Inode store?

Note : Inodes do NOT contain filenames.

• The size of the file in bytes.
• The file's physical location (the addresses of the blocks of storage containing the file's data on a HDD)
• The file's permissions.
• The Device ID
• The User ID of the file's owner.
• The Group ID of the file.
• Timestamps (ctime,mtime and atime). See FileTimes?
• A reference count telling how many hard links point to the Inode.

View Inode Information for a particular file.

For example PhilMurray's famous macaroni and cheese recipe:

$stat macaroni_and_cheese

  File: `macaroni_and_cheese'
  Size: 1965            Blocks: 8          IO Block: 4096   regular file
Device: 305h/773d       Inode: 2775423     Links: 1
Access: (0644/-rw-r--r--)  Uid: ( 1000/    staz)   Gid: ( 1000/    staz)
Access: 2007-05-16 00:21:17.000000000 +1200
Modify: 2007-05-16 00:21:16.000000000 +1200
Change: 2007-05-16 00:21:16.000000000 +1200

How to obtain a file's Inode number

• ls -i <file>